What do you guys generally use for your state management of your games?

I curious what techniques everyone employs when they write their game's state managers. Do you use a simple FSM or a HFSM or even a Behavior Tree? Was just curious because I'm messing around with a little 2D vertical space shooter and can't decide which route to take for managing the overall game states, player states and AI states.

The only one I am familiar with is FSM and that is only with minor games that are at a very small scale. I would use it for this one but I wanted to take a crack at a more medium sized game and FSM design is a pain to manage I heard at larger scales.